The present invention relates to methods of stabilizing water-sensitive clays in subterranean formations.
The recovery of fluids, especially hydrocarbon fluids, from subterranean formations may be complicated by formations that contain water-sensitive minerals capable of undergoing chemical and physical changes, e.g., minerals that swell, slough, degrade, release fines, or become ductile, when contacted with water. The chemical and physical changes to the minerals often result in the blockage and/or closure of passageways that penetrate the subterranean formation (e.g., fracture network, pore throats, etc.), thereby causing a loss in permeability of the formation. This loss in permeability impairs the flow of fluid through the wellbore and, in some cases, may even completely block the flow of fluids through portions of the formation. Loss in permeability often leads to a decrease in the production for the well. Moreover, some changes in the minerals may lead to sloughing, which yields fines capable of migrating and being produced with the formation fluids, thereby presenting potential abrasion and other problems with the production equipment and potential reduction in fracture conductivity.
One method to mitigate damage to water-sensitive minerals has included the use of cationic chemicals. Cationic chemicals are thought to, inter alia, adsorb to the negatively charged surface of some water-sensitive minerals, which to some extent blocks the water from reacting with the water-sensitive mineral. However, the resultant surface is then rendered hydrophilic, which can inhibit the flow of hydrophobic fluids like hydrocarbons. Some have attempted to provide for a more hydrophobic surface through the use of cationic surfactants. However, the surfactants may readily wash off the surface of the water-sensitive minerals in subsequent subterranean operations, e.g., acidizing or fracturing. Therefore, large quantities and multiple treatments throughout the lifetime of a wellbore may be necessary, which can dramatically increase the cost and time associated with producing fluids from the subterranean formation.